Dynamization tabs providing component interconnectivity for external fixation devices

Abstract

Dynamization tabs and methods of use are provided. Dynamization tabs may be used with an external fixation ring or other fixator device as part of a therapeutic treatment of bone fractures or malformations. The device forms a connection between one or more fixation struts and an external fixation ring so as to introduce controllable amounts of movement or dynamization to the arrangement of the struts and the fixator. By introducing controlled amounts of dynamization, therapeutic benefits can be derived in the enhanced, accelerated bone formation, mineralization and remodeling of the underlying bone. Dynamization tabs may comprise a strut connector, a mechanical biasing or dynamizing device, and a ring connector. Many different forms for introducing controlled amounts of dynamization are disclosed.

What is claimed is: 
     
       1. A dynamization system comprising:
 an external fixation ring; and 
 a dynamization tab having a longitudinal axis defined therein, the dynamization tab comprising: 
 a ring connector being configured to releasably couple the dynamization tab to the external fixation ring; 
 a strut connector being configured to releasably couple the dynamization tab to one or more struts and be positioned along the longitudinal axis of the dynamization tab in a resting position and in a manner such that it that it is capable of being displaced from the longitudinal axis under loading; and 
 a biasing mechanism, the biasing mechanism being configured to, in response to the strut connector being displaced from the longitudinal axis of the dynamization tab, apply a biasing force sufficient to return the strut connector to the resting position. 
 
     
     
       2. The dynamization system according to  claim 1 , wherein the ring connector comprises a ring connector body having a proximal end and a distal end and being positioned along the longitudinal axis of the dynamization tab, the ring connector body further comprising:
 a ring connector knob that is positioned at the distal end of the ring connector body and comprises a top surface and a bottom surface; 
 a first bore that extends from the top surface of the ring connector knob to the bottom surface of the ring connector knob and is parallel to a vertical axis of the dynamization tab, the first bore being configured to accept an adjustment screw; 
 a second bore that extends from a first upper lateral surface of the ring connector body to a second upper lateral surface of the ring connector body and is positioned parallel to a transverse axis of the dynamization tab at the proximal end of the ring connector body, the second bore being configured to accept a pivot pin; and 
 a connecting bolt that extends from the bottom surface of the ring connector body and is positioned parallel to the vertical axis of the dynamization tab and is configured to accept a connecting nut; 
 wherein the strut connector is positioned along the longitudinal axis of the dynamization tab such that the strut connector is in contact with the ring connector, the strut connector further comprising:
 a head comprising a proximal end and a distal end, the head further comprising:
 a first distal-facing surface positioned parallel to the transverse axis of the dynamization tab; 
 a locking screw aperture comprising a partial bore extending from a distal end of the head towards a proximal end of the head, the locking screw aperture being configured to accept a locking screw; 
 second and third distal-facing surfaces, each of the second and third distal-facing surfaces comprising a strut aperture comprising a partial bore extending from the distal end of the head towards the proximal end of the head, each strut aperture being configured to secure the strut connector to a strut; and 
 a ring connector aperture that is formed in the top surface of the head and extends down into the head and has an inner circumference large enough to allow the strut connector to pivot without outer walls of the ring connector knob impinging upon inner walls of the ring connector aperture. 
 
 
 
     
     
       3. The dynamization system according to  claim 2 , wherein the strut connector further comprises:
 a first arm comprising a proximal end and a distal end, wherein the first arm is positioned along the longitudinal axis of the dynamization tab and further comprises:
 a top surface; 
 a bottom surface, the bottom surface being positioned such that it is parallel to the longitudinal axis of the dynamization tab; 
 a first inner wall surface; 
 a first lateral wall surface; and 
 a first lateral pin bore extending through the first lateral wall surface and the first inner wall surface so that the first lateral pin bore is parallel to the transverse axis of the dynamization tab, the first lateral pin bore being configured to accept the pivot pin; 
 
 wherein the strut connector further comprises a second arm comprising a proximal end and a distal end, wherein the second arm is positioned along the longitudinal axis of the dynamization tab and further comprises:
 a top surface; 
 a bottom surface, the bottom surface being positioned such that it is parallel to the longitudinal axis of the dynamization tab; 
 a second inner wall surface; 
 a second lateral wall surface; and 
 a second lateral pin bore extending through the second lateral wall surface and the second inner wall surface so that the second lateral pin bore is parallel to the transverse axis of the dynamization tab, the second lateral pin bore being configured to accept the pivot pin. 
 
 
     
     
       4. The dynamization system according to  claim 3 , wherein the first and second arms are connected by a lateral member at a proximal end of the arms. 
     
     
       5. The dynamization system according to  claim 1 , wherein the ring connector comprises a ring connector body comprising:
 a first roughened surface comprising a plurality of ridges on a bottom surface of the ring connector body, the first roughened surface being positioned at a distal end of the ring connector body in a manner such that it contacts a surface of the external fixation ring and provides a frictional connection that limits rotation of the ring connector with respect to an external fixation ring; and 
 a second roughened surface comprising a plurality of ridges on the bottom surface of the ring connector body, the second roughened surface being positioned at a proximal end of the ring connector body in a manner such that it contacts a surface of the external fixation ring and provides a frictional connection that limits rotation of the ring connector with respect to an external fixation ring. 
 
     
     
       6. A dynamization tab according to  claim 5 , wherein the ring connector body further comprises a first motion limiting face positioned at the distal end of the ring connector body and parallel to a transverse axis of the dynamization tab in a manner such that the first motion limiting face is parallel and superior to the bottom surface of the ring connector body; and
 wherein a head of the strut connector comprises a second motion limiting face positioned at a proximal end of the head and in contact with a top surface of the head in a manner such that the degree of rotational displacement of the strut connector about the transverse axis of the dynamization tab is limited by contact between the second motion limiting face of the strut connector and the first motion limiting face of the ring connector body. 
 
     
     
       7. The dynamization system according to  claim 1 , wherein the biasing mechanism further comprises a compression spring positioned between a bottom surface of a distal knob of the ring connector and a bottom of a ring connector aperture such that the biasing mechanism provides a mechanical bias that opposes pivotal movement of the strut connector with respect to the ring connector. 
     
     
       8. The dynamization system according to  claim 1 , further comprising an adjustment screw disposed within a threaded bore of the ring connector that can be driven to traverse the threaded bore; wherein when a distal end of the adjustment screw is driven to impinge upon a bottom of a ring connector aperture, pivotal movement of the strut connector with respect to the ring connector is limited; and wherein when the distal end of the adjustment screw is driven away from the bottom of the ring connector aperture, pivotal movement of the strut connector with respect to the ring connector can be controllably engaged. 
     
     
       9. The dynamization system according to  claim 1 , wherein a locking-screw aperture is threaded to receive a threaded locking screw and wherein the locking-screw aperture intersects with a proximal end of strut apertures so that a proximal end of the locking screw can impinge upon a proximal end of the strut connector to prevent movement of strut fasteners with respect to the strut apertures when the locking screw is in place. 
     
     
       10. A dynamization tab having a longitudinal axis, a vertical axis, and a transverse axis, the dynamization tab comprising:
 a ring connector, the ring connector having a proximal end and a distal end and being positioned along the longitudinal axis of the dynamization tab, the ring connector further comprising:
 a ring connector body, the ring connector body having a proximal end and a distal end and being positioned along the longitudinal axis of the dynamization tab, the ring connector body further comprising:
 a top surface; 
 a bottom surface; 
 a first upper lateral surface; 
 a second upper lateral surface; 
 a first bore that extends from the top surface of a ring connector knob to the bottom surface of the ring connector knob and is parallel to the vertical axis of the dynamization tab, the first bore being configured to accept an adjustment screw; 
 a second bore that extends from the first upper lateral surface of the ring connector body to the second upper lateral surface of the ring connector body and is positioned parallel to the transverse axis of the dynamization tab at the proximal end of the ring connector body, the second bore being configured to accept a pivot pin; 
 a connecting bolt that extends from the bottom surface of the ring connector body and is positioned parallel to the vertical axis of the dynamization tab and is configured to accept a connecting nut; and 
 a strut connector, the strut connector having a proximal end and a distal end and being positioned along the longitudinal axis of the dynamization tab such that the strut connector is in contact with the ring connector, the strut connector further comprising:
 a head, wherein the head comprises a proximal end and a distal end and is positioned along the longitudinal axis of the dynamization tab, the head further comprising: 
  a top surface; and 
  a bottom surface; 
 
 
 
 wherein the ring connector can be mated with the strut connector so that a pivot pin pivotably secures to the ring connector to the strut connector and allows the strut connector to pivot about the transverse axis with respect to the ring connector; and 
 a biasing element positioned between the ring connector and the strut connector such that the biasing element provides a mechanical bias that opposes pivotal movement of the strut connector with respect to the ring connector. 
 
     
     
       11. A dynamization tab according to  claim 10 , wherein the head of the strut connector further comprises:
 a first distal-facing surface, the first distal-facing surface comprising:
 a top edge and a bottom edge, the first distal-facing surface being positioned parallel to the transverse axis of the dynamization tab and in a manner such that the top edge is in contact with the top surface of the head and the bottom edge is in contact with the bottom surface of the head; and 
 a locking screw aperture comprising a partial bore extending from the distal end of the head towards the proximal end of the head, the locking screw aperture being configured to accept a locking screw; and 
 
 second and third distal-facing surfaces, each of the second and third distal-facing surfaces comprising a strut aperture comprising a partial bore extending from the distal end of the head towards the proximal end of the head, the strut aperture being configured to secure the strut connector to a strut. 
 
     
     
       12. A dynamization tab according to  claim 11 , wherein the strut connector further comprises:
 a first arm comprising a proximal end and a distal end, wherein the first arm is positioned along the longitudinal axis of the dynamization tab and further comprises:
 a top surface; 
 a bottom surface, the bottom surface being positioned such that it is parallel to the longitudinal axis of the dynamization tab; 
 a first inner wall surface; 
 a first lateral wall surface; and 
 a first lateral pin bore extending through the first lateral wall surface and the first inner wall surface so that the first lateral pin bore is parallel to the transverse axis of the dynamization tab, the first lateral pin bore being configured to accept the pivot pin; and 
 
 a second arm comprising a proximal end and a distal end, wherein the second arm is positioned along the longitudinal axis of the dynamization tab and further comprises:
 a top surface; 
 a bottom surface, the bottom surface being positioned such that it is parallel to the longitudinal axis of the dynamization tab; 
 a second inner wall surface; 
 a second lateral wall surface; and 
 a second lateral pin bore extending through the second lateral wall surface and the second inner wall surface so that the second lateral pin bore is parallel to the transverse axis of the dynamization tab, the second lateral pin bore being configured to accept the pivot pin; 
 
 wherein the first and second arms are connected by a lateral member at a proximal end of the arms; and 
 wherein the first and second upper lateral surfaces of the ring connector can slidably engage with the first and second inner wall surfaces of the strut connector when the ring connector is pivotably secured to the strut connector. 
 
     
     
       13. A dynamization tab according to  claim 10 , wherein the ring connector body further comprises a first motion limiting face positioned at the distal end of the ring connector body and parallel to the transverse axis of the dynamization tab in a manner such that the first motion limiting face is parallel and superior to the bottom surface of the ring connector body; and
 wherein the head of the strut connector further comprises a second motion limiting face positioned at the proximal end of the head and in contact with the top surface of the head in a manner such that a degree of rotational displacement of the strut connector about the transverse axis of the dynamization tab is limited by contact between the second motion limiting face of the strut connector and the first motion limiting face of the ring connector body. 
 
     
     
       14. A dynamization tab according to  claim 10 , wherein the ring connector body further comprises:
 a first roughened surface comprising a plurality of ridges on the bottom surface of the ring connector body, the first roughened surface being positioned at the distal end of the ring connector body in a manner such that it may contact a surface of an external fixation ring and provide a frictional connection that limits rotation of the ring connector with respect to the external fixation ring; and 
 a second roughened surface comprising a plurality of ridges on the bottom surface of the ring connector body, the second roughened surface being positioned at the proximal end of the ring connector body in a manner such that it may contact a surface of the external fixation ring and provide a frictional connection that limits rotation of the ring connector with respect to an external fixation ring. 
 
     
     
       15. A dynamization tab according to  claim 10 , wherein the biasing element comprises a compression spring. 
     
     
       16. A dynamization tab according to  claim 10 ,
 wherein the ring connector knob is positioned at the distal end of the ring connector body; 
 wherein the head of the strut connector further comprises a ring connector aperture that is formed in the top surface of the head and extends down into the head and has an inner circumference large enough to allow the strut connector to pivot without outer walls of the ring connector knob impinging upon inner walls of the ring connector aperture; and 
 wherein when a distal end of the adjustment screw is driven to impinge upon the bottom of the ring connector aperture, pivotal movement of the strut connector with respect to the ring connector is limited and, when the distal end of the adjustment screw is driven away from the bottom of the ring connector aperture, pivotal movement of the strut connector with respect to the ring connector can be controllably engaged. 
 
     
     
       17. A dynamization tab according to  claim 10 , wherein a locking-screw aperture is threaded to receive a threaded locking screw and wherein the locking-screw aperture intersects with a proximal end of strut apertures so that a proximal end of the locking screw can impinge upon a proximal end of the strut connector to prevent movement of strut fasteners with respect to the strut apertures when the locking screw is in place.